Question: Expand. If necessary, combine like terms. $(1+6x)(1-6x)=$
Explanation: Notice that this expression has the following special form: $(a+b)(a-b)$ This form expands to what we call "a difference of squares": $( a+ b)( a- b)= a^2- b^2$ Using the above pattern, we get: $\begin{aligned} ( 1+{6x})( 1-{6x})&= 1^2-({6x})^2 \\\\ &=1-36x^2 \end{aligned}$